1. Field of the Invention
The present invention relates to an air bag apparatus, and more particularly, to an air bag apparatus for side crash.
2. Description of the Related Art
An air bag apparatus is provided for a car to protect the body of a rider like a driver or a passenger. As the air bag apparatuses for the car, an air bag apparatus for head-on collision and an air bag apparatus for side crash are known. The air bag apparatus for side crash is provided between a center pillar or a door and the rider to protect the body of the rider, especially, the chest of the rider.
As shown in FIGS. 1 and 2, the air bag apparatus for side crash is composed of an air bag 102 whose proximal end is stuck to a side section 101 of a seat and which expands due to gas inflation by an inflater 103 in case of side crash at a moment. As shown in FIG. 2, the air bag is folded and embedded in the side section 101 of the seat before the expansion. However, if the side direction acceleration sensor operates, the inflater 103 operates to supply a high-pressure gas into the air bag 102 at a moment. As a result, the air bag 102 expands in the direction shown by an arrow a, between the chest of the rider and the sidepiece 104 of the car to protect the body of the rider.
In such an air bag apparatus for side crash, the air bag expands rapidly at the expansion start stage, and expands gradually at the stage in which the body of the rider receives protection power from the air bag. Especially, it is desirable for the air bag shrink at that time. Such an air bag apparatus for side crash is described in Japanese Laid Open Patent Application (JP-A-Heisei 8-268213: a first conventional example). In the first conventional example, holes are opened on the middle portion of the air bag. However, because there is fear that the holes receive any damage when expanding, a perimeter of the hole is reinforced. Thus, the reinforcement effect around the hole is excellent. In the first conventional example, the reinforcement effect is achieved by the formation of the protrusion. Such a protrusion is folded and the protrusion is pushed into the inner space of the air bag. In the first conventional example, the expansion is rapid at the expansion start stage and contraction is carried out at the expansion end stage. Also, it is important that the air bag apparatus for side crash expands to a predetermined final shape at a moment in the narrow space between the rider and the side body of the car.
Another air bag apparatus is known in the Japanese Laid Open Patent Application (JP-P2000-85517A: a second conventional example) in which the proximal end of an air bag is formed with a hard member to extend and expand smoothly in a front direction. The 3-dimensional final shape of the air bag in the expansion is determined through sewing a combination of a plurality of sheets of cloth. The expansion of the air bag and the final shape depend strongly on the inner pressure and the shape of the plurality of sheets of cloth rather than the external force. Especially, the final shape of the air bag is determined based on the initial shape.
The effort to make the final shape good is shown in FIG. 3. In the air bag apparatus for side crash shown in FIG. 3, by limiting the expansion width W in the direction perpendicular to the side surface of the air bag 105 within a predetermined value, the shape on the expansion way is controlled. To make such limitation effective, an inner forming section (an inner side panel) 106 of the air bag and an outer forming section (an outer side panel) 107 are linked by suspenders or hanging bands 108 which are formed inside the air bag. By limiting the length of the suspenders or hanging bands 108 in the perpendicular direction, the above-mentioned width W on the expansion way can be determined. In this way, the width W can be limited in some degree but the angle of the suspender 108 in the perpendicular direction is instable. Such instability makes the width W in the perpendicular direction instable.
In conjunction with the above description, an air bag apparatus is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-238347). In this reference, the air bag apparatus is installed in a side door. The length of a hanging belt is longer than the length of a sewing portion.